Big Steps in the Story of Big History – Part 5

From neurons, to complex animals, to humans.

Continuing our essay series on Brian Villmoare’s “Big History” book The Evolution of Everything: The Patterns and Causes of Big History, this essay will explore how neurons came to be, and what that meant for the development of complex animals.

As we explored in a previous essay, we all run on solar power, as we derive all the energy our bodies use from things that rely on solar power in one way or another.  In this essay, we’ll explore how our bodies send communications with another form of energy, namely electricity, via specialized cells called neurons.

As Villmoare writes:

The cell that is used to communicate information in complex animals is the neuron. Scientists are still trying to understand the origins of the neuron, but the advantages are clear. A neuron uses a combination of electricity and chemistry to pass signals, and because of the adoption of electricity the signals move very rapidly. An animal that uses electricity-based communication can respond quickly to the environment, which would give it an enormous advantage over other organisms. Measurements of neuron signals in animals have found the speed to exceed 200 mph. The simplest nerve systems are found in Cnidarians (jellyfish, coral, and sea anemones). These animals possess a nerve net, in which the neurons are distributed around the animal, with no central “lump” of neurons that makes decisions. The cells communicate, but there is nothing analogous to a brain in which decisions are made. These animals tend to respond in very simple ways to a stimulus: the whole body will contract, for example, when in contact with something damaging but will not “know” the direction from which the damage came. it is important to know that the acquisition of the brain happened very early in animal evolution. Brains were possessed by Cambrian animals such as those found in the Burgess Shale, and some trilobites are preserved enough that parts of their brains have been studied … The basic cellular unit of the nervous system is the neuron, and all nervous systems on Earth, from the jellyfish to the spider to the sea turtle to the gorilla, have nervous systems composed of various arrangements and numbers of neurons. Neurons combine electrical and chemical signaling systems to transmit information from one part of the animal’s nervous system to another, and to take in sensory information from the environment and send commands to control the activity of muscles and glands … This system, in which nerve cells spread outward from a large neuron bundle, is known as a central nervous system. Central nervous systems are very old – they are seen in the animals of the Cambrian Explosion, and are visible in trilobites … These bundles of neurons tended to congregate at one end of the organism, which resulted in the cluster of sensory organs (eyes, nose, ears) developing at a “head” end of the organism. The bundle of neurons that acts as the central switching and processing station is, of course, the brain. You may have heard the insult “bird brain” thrown around among your friends (or enemies). The comparison is meant to imply that anything with a brain like a bird is unintelligent, and it is definitely not a compliment. Up until only the last few decades, bird intelligence had been almost universally dismissed, especially in comparison with mammals. However, brain researchers have been reassessing the avian brain, and it turns out that there is quite a bit more to the bird brain than we had thought. One interesting fact is that, like primates, avians have very neuron-dense brains. In fact, the avian brain is as dense with neurons as primate brains (or denser), so that the brain of a macaw (a type of parrot) has as many neurons as the brain of a baboon. The corvids (crows and magpies) also have large numbers of neurons – ravens (at 1.3 billion neurons) have as many neurons as a squirrel monkey. The problem-solving abilities of birds is now appreciated far more than in the past. Birds are known to use tools in much the way monkeys do – picking up a stick or rock to dig or break into something. In tests of consciousness, corvids have been seen identifying themselves as individuals in much the way elephants and whales do. And birds are highly trainable, which means that they have a very flexible intelligence.

But back to our story.  Early ocean creatures came to evolve limbs they could use to drag themselves ashore, and these new creatures evolved into dinosaurs:

[A]mphibians … are represented in the modern world by frogs, salamanders, and caecilians (limbless amphibians). They lay eggs in water, and have a juvenile aquatic stage (as in tadpoles), but as adults become air- breathing terrestrial quadrupeds. Modern amphibians tend to be smaller than many of the larger vertebrates, but when they first emerged from the oceans some 360 million years ago there were no other large terrestrial animals against which they had to compete. They quickly evolved to fill many of the ecological niches we today associate with modern vertebrate groups. the Triassic, and the period after that, the Jurassic, are well known as the age of dinosaurs, as reptiles filled the ecological niches that had been formerly filled by amphibians. The most well-known fossil reptile group is called the dinosaurs … This group was so diverse and so successful that they would likely still be the dominant terrestrial animal group were it not for the Cretaceous–Tertiary (K–T) Extinction. Roughly 65 million years ago, a large meteor hit the Earth in what is now the Gulf of Mexico. This enormous meteor caused a large flood in North America, and threw enough silt into the air to block photosynthesis for roughly a hundred years. The lack of photosynthesis caused the food web to collapse, and all of the large terrestrial animals on Earth went extinct … Figure 9.4 Extinctions. This classic early twentieth-century (1910) illustration, from Ernst Haeckel, does a good job of showing the importance of extinctions for understanding our current animal diversity. On the right margin I have added the names we now attach to the extinction events. As is visible in this illustration, the radiation of large animal groups, such as the reptiles and mammals, was only possible once an extinction event had cleared the path. Not all groups have thrived just because another group was reduced by an extinction event, but those that had an adaptive advantage (such as the reproductive advantage in mammals) were able to thrive once the dinosaurs were no longer filling all the available ecological niches. The causes of extinctions are under study by paleontologists and geologists, as we only know the cause of a few …Many of these animal groups ultimately did recover, although, in many cases, not in their original forms. For example, one branch of the dinosaurs, the saurischians, are represented in today’s birds. Some groups persisted largely as they were, as in the crocodile and turtle groups. And some simply went extinct, as in the large ocean-going reptiles (mosasaurs, ichthyosaurs, and pliosaurs), and the ornithischian dinosaurs. But one group that had formerly been relatively marginal suddenly exploded.

After the dinosaurs largely went extinct, there was room for mammals to grow:

The mammals, with their high reproductive rate and their maternal care of offspring, were able to rebound from the extinction event and fill the niches formerly filled by the dinosaurs. Mammals evolved in stages, and, remarkably, there are three kinds of mammal alive today, representing ancestral and more evolved forms. We still live in the age of mammals …

Villmoare remarks on the evolution of the animal jaw from what used to be gills:

[T]he evolution of the bony mandible was a more remarkable evolutionary transition. Unlike the cranial vault, which is simply a group of hardened plates, the mandible acts as a hinged joint, articulating against the upper jaw. Where did the jaw come from and how was it acquired? Surprisingly, the answer does not come from fossils, but rather from examining the embryos of existing animals. Evolution often works by changing the organisms through development, and, because the ancestor of all existing jawed vertebrates was a fish, we all go through a fish stage in our development. If you look at the embryos of fish, reptiles, rats, and humans, we all look essentially similar early in our developmental stages. This reflects our fish ancestry. Because we have a “fish stage,” we also have gills. During the various developmental stages, the bones supporting these “gills” (the gill arches) shift into the head to become our upper and lower jaw. In jawless animals, such as lampreys and hagfish, this transition never occurs; the gills remain gills throughout development, and they continue like that through their adult stages. In jawed vertebrates, the top two sets of gill arches shift to become the jaws. This transition can be directly observed in developing organisms …

Villmoare then describes the development of uniquely four-limbed vertebrates (animals with backbones):

If you look at the bones of your arms and legs, you may notice that they share a pattern. There is one upper bone (the humerus in the arms and the femur in the leg), then two lower bones (radius/ulna in the arm, and the tibia/fibula in the leg), then the same number of wrist/ankle bones and the same number of hand/foot bones. This is not an accident. At some point around 400 million years, lobe-finned fish had only forelimbs, then the forelimb was essentially copied to make the hind limb, and the genetic controls were copied when the limb itself was copied. The group of organisms with four limbs are known as tetrapods (from the Greek for the number four, plus the word for limb). Interestingly, this replication occurred only once in evolutionary history, to the best of our knowledge, because there are no six-limbed vertebrates.

Some mammals developed into primates, and later into humans:

One of these mammalian lineages, the Primates, was a group of small, arboreal (tree-living) animals who survived by eating insects. They probably lived in flowering trees that attracted insects trying to pollinate the trees. We know that they were insectivores because they were so small – large animals have a hard time tracking down enough insects to maintain a large body (unless they are eating social insects, as anteaters do). Also, these small creatures had sharp, spikey teeth for cutting through the hard insect shells. Their eyes faced forward for good binocular vision, much as we see in carnivores today (compare an owl’s eyes to a pigeon’s). bipedalism is one of the key traits that characterizes our lineage. By about 4 million years ago we have a good fossil record of a truly bipedal human ancestor, Australopithecus. Although we often think of brain size as the critical difference between apes and humans, in fact the earliest humans had brains no larger than modern chimps. We see two critical adaptations appear when our brains jump a bit in size, as it is likely that these two changes enabled the expansion of our brains. And these two differences are not in the skull at all – they are the hands and feet. Ardipithecus, which is known from deposits 5.2–4.5 million years old, has an opposable big toe, and an ape-like hand with a thin, short thumb. But by about 3.9 million years ago, with the appearance of Australopithecus afarensis, we see a brain that is about 30 percent larger than a chimp’s. This brain increase is accompanied by a change in the hands and feet. It is worth exploring the details of these differences because they may well have been the key changes that enabled us to become the big-brained apes we are today. So we have good hand strength, thanks to our thumbs, but we also have precision. When you thread a needle, your thumb and forefinger are in precise opposition. Humans can make very fine movements with their fingers and thumb. Writing with a pencil is another example. None of these things are possible for chimps. With their long fingers and short thumbs, they cannot hold anything small with precision and strength. This may well have been one of our critical adaptations, because making tools is what we do well. While chimps can make a few tools, our hands allow us a great deal more precision. Our seemingly weaker hands give us a huge advantage in making stone tools. Our other major change is in our feet. All apes have opposable big toes, and this is a critical adaptation to climbing in trees. If you have ever tried to climb a tree, you know that even if your hands can easily pull you up, you will tire quickly if you can’t find some way to help yourself with your feet. Apes can simply grab a limb with their feet. The human foot has a big toe that is in line with the other toes and is essentially useless for climbing. The advantage of having a big toe in line with the other toes is that it can be used for terrestrial locomotion – walking. Humans use their big toes every time they take a step but especially when running. Humans are very efficient walkers and runners. Quadrupeds are faster, even small quadrupeds are fast. Anyone who has seen someone trying to catch their small dog in the park knows that humans are slow and clumsy in comparison to quadrupeds. However, we are very, very efficient. In comparison to a chimpanzee knuckle-walking, a human uses roughly 1/7th the energy to cross open ground. In a climate where forests were drying out and becoming patchy, the ability to efficiently cross a grassland to get to another forested patch to find food would have been a critical adaptation. And humans are able to do this steadily. Well-conditioned humans today are able to walk or run 50 or even 100 miles (160 km) essentially without stopping. The shape of our feet is essential for this, as the big toe allows the foot to act as a lever and shock absorber while walking and running. The big toe generates most of the propulsive force, and is essential to any movement except the slowest stroll. Often, fossil species, especially dinosaurs, are known from only a single fossil. But when we examine living species we want to know all kinds of things that can only be known by looking at the variation in anatomy and behavior across the species. For example: How big or small can they get? Are males larger than females? How long are the juveniles dependent on the parents? How large are the social groups? What kind of social group does the animal have? We can rarely access this kind of information for fossil species. However, several species of early humans have such good fossil records that we can examine exactly those important parameters we normally only study in extant species. When the climate changes and habitat disappears there are two responses by organisms: go extinct or adapt. Most organisms simply go extinct (more than 99.9 percent of all species that have ever existed are extinct), but obviously some do persist. We are fortunate that humans found a way to adapt.

Humans came to be distinguished from chimpanzees:

Figure 11.1 Comparison of human and chimpanzee skeletons. Both have the exact same number of bones, and the bones perform the same functions, indicating their shared ancestry. The differences are in the shapes of some of the bones. For example, the human has short arms but long legs, and in the chimp this is reversed, reflecting their different locomotor modes. The human, in its long legs, short arms, and voluminous lung capacity, is particularly well adapted to long-distance terrestrial locomotion, even as it lacks the powerful shoulders and arms of the chimp. Figure 11.2 A comparison of Australopithecus (left) with early Homo (right). Note the continued trajectory of human evolution – early Homo has a smaller face and larger braincase than Australopithecus, which is the pattern established in our lineage by about 4 million years ago. The subsequent species Homo erectus has an even bigger braincase and smaller face, as do we (Homo sapiens), with the largest braincase relative to the face. This pattern of change reflects the decreased use of our faces as tools (for fighting, or tearing open hard foods), and the increased dependence on our brains to generate, design, and build tools out of materials found in nature.

This divergence from chimpanzees led to various aspects of human uniqueness:

The complete anatomical commitment to a terrestrial lifestyle did not come until Homo erectus. With this change came a suite of major alterations to the body. We saw that the upper limbs became smaller and the lower limbs longer, and this allowed a significant increase in bipedal efficiency. But there were other changes that reflect the fact that we have become efficient long-distance runners. The rib cage, which in apes is shaped like an inverted funnel to allow for the heavy shoulder musculature, changed to a “barrel” shape to accommodate much larger lungs. Even a small chimpanzee has stronger arms than the strongest power-lifting human. In the 1920s, at Bronx Zoo, an agitated female chimpanzee (at roughly 90 pounds/40 kg) performed a 1,200 pound (540 kg) deadlift with one arm. No human, even modern weightlifters, has ever approached that level of strength. The muscles and bones of apes are built for raw strength, to suspend their bodies and catapult them through the trees. That kind of strength seems useful, so why would we lose it? Humans have acquired something else by sacrificing raw strength: speed. A trained human adult can throw a baseball between 60 and 90 mph (100–145 kph). Our arms and shoulders have reorganized the anatomy to give us the ability to project force at a distance. This is a relatively rare phenomenon in nature – only a few animals, such as spitting cobras, can defend themselves or strike prey without exposing themselves to danger from physical contact. This ability would have given us a significant advantage over other animals, whether hunting or defending ourselves against large predators. These major transitions first appeared with Homo erectus. Combining the overall increase in body size to that of modern humans with the locomotor efficiency of the lower body, and alterations to the shoulder that make throwing more efficient, Homo erectus was a formidable predator. This was the first time that humans were able to hunt prey and to defend themselves against other predators on the open savannahs of Africa. This shift in physical abilities compatible with open country survival and locomotion, along with a 50–100 percent increase in brain size, made Homo erectus able to adapt to a much wider variety of climates, and in a relatively short time after it evolved its anatomy we suddenly see it appear in the fossil record of Asia and Europe. Because of these reasons, for many researchers Homo erectus is the first hominin that we recognize as “us.” Between 250,000 and 150,000 years ago, we see a change in the archaeological and fossil record. Over a period of some 100,000 years there is a shift toward technological sophistication that was not present previously. This change, called the Middle Stone Age transition is a departure from the relatively unchanging archaeological record of the previous 1–1.5 million years. It is during this time that our species, Homo sapiens, appears in the fossil record, first in Africa, then, over some 50,000 years, around the world.

At some point, animals, and later early humans, developed the ability to count. As Andreas Wagner writes in Sleeping Beauties:

Among all the fundamental human abilities that underlie our civilisation, mathematics stands out. From its humble origins in Mesopotamian trade and taxation, it became the foundation of modern technology. And more than that, it helped formulate laws of nature that reach all the way down to the structure of subatomic particles, all the way up to the cosmos, and all the way back to the first days of the universe. Mathematics reveals principles that hold not just on our planet, but on any planet in our galaxy – or in any galaxy. Little surprise then that scientists are wondering where maths comes from. And they find that maths builds on an ancient talent that has been slumbering for most of humanity’s history … In an even simpler experiment, a psychologist places two small, opaque buckets next to an infant sitting on the floor. The buckets are far enough away that the infant cannot reach both at the same time. While the infant watches, the experimenter drops one graham cracker into the first bucket, and two crackers into the second bucket. Infants as young as ten months reach or crawl towards the bucket with more crackers. They know that two crackers are more than one. Infants can already do basic maths before they can speak. Experiments with infants, children and adults reveal that all of us are empowered with two number skills that are either innate or that develop in infancy. Both quantify numerosity, the number of objects in a set of objects. The first allows us to count small numbers of objects instantly and without being aware that we are counting. It’s called subitising, from the Latin word subitus for sudden. Subitising works for up to three or four objects without any training … [E]xperiments revealed truly profound maths-related talents in animals. Baboons live in large troupes of up to a hundred individuals that travel large distances to search for food. When they do, the troupe sometimes splits into smaller groups that merge again later. How do individuals decide whether to join one or the other group? Perhaps they follow one or the other leader, some high-ranking individual in the group? But no. A 2015 study of baboons equipped with GPS-trackers showed that individual baboons do not just follow a leader. Instead, they prefer to join the larger of two groups, perhaps because there is safety in numbers, perhaps because larger groups forage more efficiently. But how does a baboon identify the larger group? Like a person who needs to decide in a flash, a baboon does not count large numbers. It estimates. In fact, a baboon’s ability to distinguish two different numbers is similar to that of a three-year-old human. In other words, baboons, like humans, have a number sense. Monkeys are not even the only animals with a number sense. American black bears can estimate the number of dots presented on a touch screen. Field mice prefer to prey on smaller groups of red ants than on larger ones. Lions estimate the size of another group of lions before attacking them. Crows choose more over fewer morsels of food. Guppies prefer to join the larger of two shoals. Male mosquitofish prefer to join groups with many females. Male frogs count how many mating calls other nearby males produce, and match their number – if a neighbour calls five times, they’ll call six times to impress the girls. Perhaps the most painful discovery for the human ego: even spiders and insects with their tiny brains have a number sense. Spiders know the number of prey in their web, bumblebees register the number of flowers on a single plant, and honeybees remember the number of landmarks they pass on their way to a flower patch. It’s easy to understand how organisms that need not count their change can benefit from a number sense. A bumblebee that counts the flowers on a plant need not waste effort to visit the same flower twice. A crow that scouts the ground for patches with many grubs will go hungry less often. A fish that joins a larger shoal is more likely to survive a predator attack. A lion that attacks a smaller group of animals is less likely to get hurt. Because humans and crows process numbers in brain regions with different evolutionary origins, their number sense must also have evolved independently. For the same reasons, bees can lay claim to yet another independent invention of the number sense. These multiple discoveries teach us that a number sense must be broadly valuable for survival … [A] number sense does not require a complex brain. Honeybees, for example, have a mere million neurons compared to our billions. And even that may be much larger than necessary. When neurobiologists simulated the neural networks of a simple animal brain in a computer, they found that a network with as little as six hundred neurons can develop a number sense.

Meat eating played a big part in human development, especially the development of the human brain.  As Villmoare writes:

The adaptation to meat was probably critical, because brain growth requires enormous resources and meat is highly dense in calories, fat, protein, and amino acids. In fact, becoming more reliant on meat may have enabled the brains of early species of Homo to evolve to above 600 cc. This shift to meat dependence may have been the key to our later success. And with a relatively slow bipedal gait, it was unlikely that these humans could catch prey directly. But the savannah ecosystem has a large niche for meat scavengers – after a kill, hyenas, jackals, vultures, crows, and a variety of other animals feast on what is left behind after a lion kill. The remains of animals eaten by early Homo show cut marks that are on the types of body parts ignored by lions (who get first pick), but eaten by hyenas. So humans were in the scavenger niche, much as hyenas and jackals are today. There is ample evidence for adaptation to meat eating. This is the time period when we first see evidence of stone tool manufacture and cut-marked bones; further, the DNA of human parasites are closely related to the DNA of carnivore parasites, and the parasite lineages appear to have diverged between 2 and 3 million years ago. Suddenly we could feed our evolving brains. And once the brains evolved further, that of course meant that ever more complex problem-solving abilities were available. This became a feedback loop, as more complex behaviors enabled greater acquisition of meat, and the additional meat enabled more brain development. Repeated over and over, the brains of the genus Homo more than doubled from 2 million years ago to today. Around 250,000 ago our skulls reached their current shape and size. However, the technology associated with these early modern humans is not different from what we see at 300,000–750,000 years ago, associated with earlier human species. These earlier humans (sometimes called Homo heidelbergensis) have brains a bit smaller than ours, but they are still quite large (larger than 1,200 cc), and in fact they have some overlap with modern human brain size. Researchers had expected that there should be some kind of an identifiable change in technology once modern humans evolved. In a way, this is a form of self-fascination or egotism: since we are so intelligent today, we must have been smarter than anything that came before. But this is not what the archaeological record shows. Rather, the earliest modern Homo sapiens had technology identical to what had been prevalent for the previous 500,000 years. Paleolithic archaeologists had long seen a shift to more advanced technologies around 100,000 years ago, including the first appearances of fishhooks, shell-fishing, long-distance exchanges of goods, beads, and art … It is extremely unlikely that the first appearance of any innovation would be preserved in the fossil record, so new technologies would only ever be preserved once they were relatively common … Increase in brain size was probably enabled by our transition to eating meat and animal parts some 2.6 million years ago. The brain is a very expensive organ, metabolically speaking. A chimpanzee uses roughly 8 percent of its metabolism supporting the 350 cc brain, and a human uses ~25 percent of its metabolism keeping the brain fed. Today, we have little trouble finding enough calories, now that we have industrialized agriculture with domesticated grains and animals. But at 3 million years ago, Australopithecus was not a meat-eater, and with a diet of natural vegetation could not have supported a large brain. At 2.6 million years ago, humans had started to scavenge meat from kills, and today archaeologists find cut marks on bones from those temporal horizons, along with early stone cutting tools. This is when the human brain gradually started substantial evolutionary growth. As humans became more and more dependent on meat, their brains grew, enabling more sophisticated techniques for acquiring food. These more sophisticated techniques (such as organized hunting and projectile weapons) would have enabled the acquisition of more food, enabling more brain growth. This cycle became a feedback loop, and humans became more and more encephalized (large brained) over the next 1.5–2.0 million years.

Meat eating and larger brains led to accelerating human technology, especially as population increased dramatically:

Humans, who had ready access to meat, and who were under pressure to solve complex resource-related problems, as well as store important social information, developed larger and larger brains. In terms of time intervals, the changes occurred over tens and hundreds of thousands of years, but at some point humans developed skills that allowed them to survive almost anywhere on Earth. Once populations of humans were distributed across the Old World (Africa, Asia, and Europe), subsequent population growth increased population densities rather than causing migrations. It was probably at this point that demography (population density) became a major factor in the spread of technology. Imagine you are a young modern human (Homo sapiens) living comfortably somewhere in East Africa, with very low population densities.  Your social group is probably your own family: your parents and siblings, and potentially some uncles and aunts. If you want to learn how to make stone tools, or spears, or fishhooks, you only have a few adults who can teach you. However, if the population increases, such that your area includes another five or ten families within walking distance, you might be able to look around to see who makes the best fishhooks, for example, and learn from that person. Suddenly, you have access to a more sources of knowledge. And, as you become an adult, you in turn become a source of information for younger humans in nearby families who want to know how to make the best fishhooks. Repeated over thousands of generations over millions of square miles, the increased population densities of modern humans pushed technology steadily forward. With relatively high population densities, innovative information could literally travel around the world. This pattern actually repeats over and over throughout human history, and is why cities become centers of innovation. And when civilizations collapse and population densities decrease (as in the fall of ancient Rome), technologies can become lost.

As Gregory Cochran and Henry Harpending write in The 10,000 Year Explosion:

Naturally, increased population size had a similar impact on the generation of new ideas. All else equal, a large population will produce many more new ideas than a small population, and new ideas can spread rapidly even in large populations. In Guns, Germs, and Steel, Jared Diamond observed: “A larger area or population means more potential inventors, more competing societies, more innovations available to adopt— and more pressure to adopt and retain innovations, because societies failing to do well will be eliminated by competing societies.” We take this observation a step further: There are also more genetic innovations in that larger population … Several technological innovations are associated with Homo erectus. Perhaps the most well known is the “Acheulean hand-ax.” The interesting difference between Acheulean tools and the earlier “Olduwan” tools is not so much their function but their appearance. Early Homo made tools that had very sharp edges, but there was no underlying design. A few rocks were knocked together until a sharp edge was achieved, and then it was used. Acheulean hand axes, in comparison, all have a similar design: they are teardrop-shaped, and rather than a few whacks necessary to make one, it must have taken considerable skill and a longer time. This tool technology reflects an increase in mental sophistication in two ways: first, the tool-maker is clearly making the tool to match a mental template; and second, there is a significant increase in skill necessary to make this tool. All of this speaks to the increased intellectual power of Homo erectus … By roughly 150,000 years ago, the modern humans in Africa had acquired significant technological and behavioral advantages over all the other species of humans across the world. Over time, these modern humans migrated out of Africa and spread out across the continents of Asia, Europe, and Australia (North and South America were not populated by humans until much, much later), ultimately replacing the local populations (derived from Homo erectus, as in the case in Asia, or the Neanderthals in Europe). There is a group of technologies that appears only with the evolution of modern humans. Tools like fishhooks (made from bone or shell), bone needles (used for sewing hide clothes), and more sophisticated stone blade technologies first appear in the African fossil record when modern humans arrive, and then appear elsewhere only with the arrival of modern human populations migrating out of Africa. it is the ability to communicate so effectively that may have given humans their ultimate advantage. Language is the natural human method of communication, and language permits the transmission of extremely complex ideas. You can imagine the advantage this would give the early modern humans over any other human species. The ability to explain to others of your group where the game herds were, and provide a geographic description of an area, for example, would allow you to exploit the game animals much more efficiently than earlier human species. Methods for innovative technologies could be explained verbally, and readily passed from group to group. Dangers could be explained in detail, and plans made for dealing with them.

Beyond better technology, humans came to be able to communicate abstract ideas, which made the communication of new ideas to others much easier.  As Villmoare writes:

At roughly the same time that we see the appearance of innovative Neolithic technologies, we also see the representation of abstract ideas. This is most visible in the art of early modern humans across the globe. This art takes several forms: cave paintings, petroglyphs pecked into cliff walls, and figurines. In all of these art forms, there are clearly ideas being expressed, much as we see in art today. This ability to take an idea or thing and portray it visually represents an important advance that probably allowed humans to outcompete all other human species across the globe. In all likelihood it is associated with the same intellectual advancements that give us language. Language is, after all, an abstract representation of ideas. Other animals can communicate using sounds, but as far as we know only Homo sapiens has the ability to create a true language, in which sounds represent any idea even though they sound nothing like the idea itself. Figure 11.3 Rock art. Here we see ancient (25,000–50,000 years old) rock art from Australia (top), Africa (middle), and Europe (bottom). The appearance of rock art is one of the surest indicators that modern Homo sapiens has evolved, and that it is something fairly distinct in its behavior from previous species. No other human species makes clear, representative art. We tend to associate the appearance of rock art with the appearance of language, since they are both ways of representing specific ideas. Increases in brain size are likely responsible for this ability to “abstract” ideas and communicate them effectively. When a child calls a train a “choo choo,” that child is representing the object using something that “sounds” like the idea. But when, as an adult, you call a train a “train,” there is nothing in that sound that is particularly train-like. It is an abstract representation of an idea. That is a particularly powerful ability, because it means all manner of ideas can be represented and communicated to other people. In fact, one of the characteristics of language is the ability to shuffle and reorganize words in ways that communicate new ideas not necessarily related to what is in front of the speaker.

In the next essay in this series, we’ll explore how fire, and cooking with it, sparked an explosion that blew up the human brain.